Cast sand seal skirt rings



A ril 21, 1964 J. A. WILSON CAST SAND SEAL SKIRT RINGS Filed Aug. 8,1960 INVENTOR John A. \Vi l son.

0 m w 0 a v ATTORNEY United States Patent 3,129,934 CAST SAND SEAL SKIRTRINGS John A. Wilson, Griiiia, Qntario, Canada, assignor to FahrailoyCanada Limited, ()riiiia, Ontario, Canada Filed Aug. 8, 196%, Ser. No.48,138 1 Claim. (Cl. 263-49) This invention relates to cast sand sealskirt rings for incorporation in inner covers used in the heat treatmentof coiled steel strip in cover type annealing furnaces.

Skirt rings of this type are usually formed of wrought materials. Suchconventional skirt rings not only have limited strength and rigidity butthey frequently become distorted or damaged in use due to thetemperature stresses to which they are subjected. Moreover, inner coversusing the standard skirt rings tend to go out of round and requireregular servicing to press the skirt ring end of the cover back intotrue circle.

It is an object of this invention to provide a skirt ring which issimple in structure, easy to manufacture, and inexpensive to produce,which possesses higher strength characteristics and greater rigidity,which absorbs heating and cooling stresses without distortion, and inwhich cracking tendencies are substantially eliminated, whereby theinner cover associated therewith maintains its shape during operation,and whereby the service life of the inner cover is significantlyprolonged.

The invention resides in a cast skirt ring comprising a flat circularring portion having a flat unobstructed upper surface for reception ofan inner cover, and an inte gral leg depending from the outer edge ofsaid ring.

The invention will be described with reference to the accompanyingdrawing, in which FIGURE 1 is a sectional elevation of a cover typeannealing furnace having incorporated therein a skirt ring of thepresent invention,

FIGURE 2 is a partial plan vieW of the skirt ring of the invention, and

FIGURE 3 is a sectional elevation of the skirt ring.

In the drawing, 1 is a cover type annealing furnace such as is used inthe heat treatment of coiled steel strip in basic steel mills. Thefurnace comprises a base 2, fan 3, an outer cylindrical refractory linedcover 4 carrying heating elements 5, and a cylindrical inner cover 6,all in accordance with conventional structure. The coils of steel stripunder treatment are indicated at 7. In usual practice, the outer coveris lifted off the base by means of a crane, and the pile of steel stripis built up on the base. The inner cover is then lowered over the pileof strip and the outer cover finally dropped over the whole assembly.

The heating elements provide the source of heat which is transferredthrough the inner cover to the coils of strip, which are heated to thedesired annealing temperature. The fan 3 provides for the recirculationof atmosphere gas within the inner cover, thus accelerating the heatingof the charge through convection heat transfer.

The inner cover is normally fabricated out of carbon low alloy steel orstainless steel.

A skirt ring 8 is Welded to the lower open end of the inner cover and isarranged to seat in the sand 9 of an annular sand trough 10 in the base.It will be evident that the inner cover provides a confined protectiveatmosphere to reduce the seating of the strip and exclude external air.

In accordance with the invention, the skirt ring 8 comprises a flatcircular ring portion 8a having a flat unobstructed upper surface 8b forreception of the edge of the inner cover 6. A circular leg 11 dependsfrom the outer edge of the ring portion 8a, such leg being con tinuouslycorrugated with corrugations 12 which extend laterally from the ringportion 8a to the free edge of the leg. Preferably, a plurality ofstiffening gussets 13 connect the outer surface of the leg with theunder surface of the ring portion.

The skirt ring 8 comprises a plurality of uniform arcuate or segmentalsections 14 welded together at their abutting end edges.

Each section 14 is composed of cast steel, such as plain carbon orstainless steel.

The use of castings, rather than Wrought metal, in the formation of theskirt ring has many advantages. It permits greater economy ofconstruction and provides higher strength characteristics and greaterrigidity, thus greatly contributing to the maintenance of the shape ofthe inner cover in operation. Moreover, the use of castings permits theuse of the stiffening gussets 13 at very small extra cost as comparedwith a fabricated structure.

Since stress cracks tend to develop and work radially inwardly from theouter diameter of the angle flange or leg of skirt rings, the locationof such flange or leg on the outer edge rather than the inner edge ofthe cover receiving ring portion substantially eliminates crackingtendencies and thus adds significantly to the service life of the innercover. I

An important feature resides in the corrugation of the vertical leg 11.These corrugations add markedly to the strength of the skirt ring andassist in absorbing heating and cooling stresses without distortion ofthe ring.

I claim:

A unitary inner cover for an annealing furnace, comprising, acircumferentially-continuous cylindrical wall having a vertical axis ofsymmetry and a top secured to and closing the upper end of said wall,and a circular skirt ring reinforcing the open circular lower end ofsaid wall, said ring comprising first and second portions integral witheach other, said first portion being a horizontally planar annuluscoaxial of said axis and having an outer diameter slightly greater thanthe corresponding diameter of said wall, the lower edge of said wallbeing fixed to and supported on said first portion, said second portionbeing a cylindrical skirt depending vertically from the outer peripheryof said first portion normally thereto, said ring forming the solesupport for said cylindrical Wall, the wall of said second portion beingcontinuously vertically corrugated throughout its peripheral extent,said skirt ring being formed from a plurality of cast metal segmentsintegrally united in end-to-end relation to form a continuous circularring, and a plurality of vertical, reinforcing plates disposed generallyradially of said axis and in equiangularly-spaced relation thereabout,each said plate being integrally connected with the inner surfaces ofsaid first and second portions, respectively.

References Cited in the file of this patent UNITED STATES PATENTS1,961,221 Hunter June 5, 1934 2,144,374 Hoffman Jan. 17, 1939 2,145,074Dreifein Jan. 24, 1939 2,233,580 Breedon et a1. Mar. 4, 1941 2,260,214Deahl Oct. 21, 1941 2,414,530 Jacob Jan. 21, 1947 2,854,226 Cone Sept.30, 1948

